The present invention relates to a fan driving circuit using a Pulse Wide Modulation (PWM) signal. More particularly, by means of a control signal at a buffer period, when phase changes, power-consuming would be reduced. The fan motor can change phase successfully and operate efficiently for power-saving, capacity-improving and cost-reducing.
A control circuit for heat-dissipation system in Taiwan Patent No. 507973 discloses a conventional fan control circuit using a PWM signal. The control circuit includes a signal generator electronically connecting to the heat-dissipation system, providing power of the heat-dissipation system and generating a control signal to control the ON/OFF of the power; and, a power regular apparatus, electronically connecting between the heat-dissipation system and power, paralleling to the signal generator, provides constantly basic power for the circuit of the heat-dissipation system to prevent signals outputting from external devices electronically connecting to the heat-dissipation system from being interfered by the control signal.
Although the fan driving circuit using a PWM signal mentioned above can prevent signals outputting from external devices electronically connecting to the heat-dissipation system from being interfered by the control signal, it is insufficient for the control circuit in real practice. Fan motor must change phase first when operating. The output wave diagrams of phase change when fan motor uses the above control circuit or other conventional control circuits are shown in FIG. 7 and FIG. 8. As shown in the above diagrams, the waves when the fan motor changes phase is successive. Therefore, conventional fan driving circuit using a PWM signal tends to power-consuming increasing by fan motor changing phase. Since the required power for the fan increases, it is impossible to save power and operate the fan efficiently. That is, when changes phase, the fan motor is unable to change phase successfully, resulting in low efficiency.
The main objective of the present invention is that when phase changes, by means of a control signal at a buffer period, power-consuming would be reduced. The fan motor can change phase successfully and operate efficiently for power-saving, capacity-improving and cost-reducing.
To achieve the above objective, the present invention provides a fan driving circuit using a pulse width modulation (PWM) signal. Wherein, a signal generator electronically connects to a fan motor and provides power for the fan motor. The signal generator generates a control signal for controlling ON/OFF of the power. Wherein, the signal generator generates a control signal at a buffer period when the fan motor changes phase for controlling phase change. Therefore, when phase changes, by means of a control signal at a buffer period, power-consuming would be reduced. The fan motor can change phase successfully and operate efficiently for power-saving, capacity-improving and cost-reducing.